Battery - I plan on testing 8s -12s to see what i can get away with.
ESC - Swordfish Pro 300A (should give me a fair amount of headroom)
Motor - TFL SSS 56mm (exact spec not decided yet)
Gearbox - The options are either a torqeedo 14:1 or a Reisenauer Super Chief (this will depend on the prop/impeller size and motor)

Motor unit/housing
I still haven't decided exactly which route I am going to take here. The initial unit will be 3D printed in order to keep the costs to a minimum.
Jet-drive: To start I will go this route. I will use a 60mm-64mm impeller. This may make it possible to get away without a gearbox, simplifies the system and makes it cheaper. It will be less efficient, but to start with I don't mind.

Prop with Kort nozzle: Using a gearbox to lower the prop RPM will allow me to use a larger prop and thus make the drive more efficient! However this means that there are more parts to fail and also increases the cost of the build.

Way out approach: I recently saw a video of a 3D printed brushless motor. Therefore it would be possible to design a integrated motor/propeller unit and then custom wind it. This would be a really interesting approach, but I must admit that I may be a bit lazy for this.

My steps for the project will be as follows:
- Design and build the foil.
- Design, build and test the motor unit. I have a k1 kayak and surfboards I can test on to at least ensure it works and provides enough power and speed.
- Hack the windsurfer and attach the foil.
- Attach motor unit and then test to see what happens!

Thanks @Jezza great start
I plan on a similar tack as yourself, great heads up on the windsurfer so thanx, but I am going to hunt out a low kv motor and tie it to an big 12s.
Alien power systems offer a 100mm custom KV, I can probably Ali up a supplier also.. GL all

Bazaki wrote:I do have the 14:1 ism gearbox from torqeedo laying around and thought about a flier 420a esc and a TP 5860 or 70 motor,

But a good housing, i have no idea yet.

Which torqeedo model is the gearbox for? And could you possibly give me dimensions for it?
I think that with a gearbox like that, you could almost get away with a 2000W motor and a 200mm prop. I half want to get on just to experiment on whats possible!

hardwiring wrote:Thanks @Jezza great start
I plan on a similar tack as yourself, great heads up on the windsurfer so thanx, but I am going to hunt out a low kv motor and tie it to an big 12s.
Alien power systems offer a 100mm custom KV, I can probably Ali up a supplier also.. GL all

The only problem with a 100mm motor, is that is almost twice the drag of a 56mm. You'll also need a larger prop because of the drag. I think that the 56mm is maybe the ideal size.
How low do you want the KV?

Jezza wrote:
The only problem with a 100mm motor, is that is almost twice the drag of a 56mm. You'll also need a larger prop because of the drag. I think that the 56mm is maybe the ideal size.
How low do you want the KV?

Thanks, coming at this with Esk8 experience and I have not considered drag. In Esk8 there is an sweet spot of battery S to kv, very basically high s lower kv. Don't believe this is all about the ESC that we use but I am often wrong so assumed 10s 190kv , 12s sub 150kv .... that 14 to 1 box looks good, guess could be tough to find my side of the pond.

If you look at the above 3 combinations, you can very quickly see how increasing the RPM allows you to use a smaller prop size. If you go for 2500rpm, I'd say you'd want a prop size of around 200mm.
The big thing to me is to try use readily available parts that can be obtained relatively easily. I'll most likely over spec the motor and ESC allowing me to test multiple configurations and drive systems.

hardwiring wrote:

Jezza wrote:
Thanks, coming at this with Esk8 experience and I have not considered drag. In Esk8 there is an sweet spot of battery S to kv, very basically high s lower kv. Don't believe this is all about the ESC that we use but I am often wrong so assumed 10s 190kv , 12s sub 150kv .... that 14 to 1 box looks good, guess could be tough to find my side of the pond.

What S for 2000kv??

If you are UK based, torqeedo stuff is quite easy to get as its all based in Germany. The RC boat scene is also huge in Germany so that's where most of the parts will most likely come from.
2000kV will be too high. I dont think you'll be able to get enough voltage to generate a sufficient amount of power and torque.

The preferred configs tend to be 320KV motors at 50V for 64mm jets (jet surfboards that is). A hydrofoil will use way less power once up.

I'll most likely get a motor around 790KV and then gear and prop it accordingly.

Design is still changing a lot. I use Fusion 360 to model components and I am trying to 3D print most parts. I have a pretty powerful SSS54104 500kv motor, and just added a 7:1 planetary gearing from Parker. Brings my prop to about 2500rpm with a 10S setup. I'll start with a 13cm printed prop and see how that goes. I can later print different prop sizes / shapes and tune performance.

I plan to use a Liquid Force aluminum mast and will attach to my RRD K-race 70 kite race board which has been collecting dust in the garage. Will hollow the board and put batteries and ESC inside. Probably add a big aluminum plate as heat sink for cooling the ESC. My parts list is here: https://www.dropbox.com/s/d31ti8819uahm ... .xlsx?dl=0

Hope to get this in the water soon but there are still a few challenges ahead. I look forward to continue hearing what everyone else is doing and discovering. Aloha!

Design is still changing a lot. I use Fusion 360 to model components and I am trying to 3D print most parts. I have a pretty powerful SSS54104 500kv motor, and just added a 7:1 planetary gearing from Parker. Brings my prop to about 2500rpm with a 10S setup. I'll start with a 13cm printed prop and see how that goes. I can later print different prop sizes / shapes and tune performance.

I plan to use a Liquid Force aluminum mast and will attach to my RRD K-race 70 kite race board which has been collecting dust in the garage. Will hollow the board and put batteries and ESC inside. Probably add a big aluminum plate as heat sink for cooling the ESC. My parts list is here: https://www.dropbox.com/s/d31ti8819uahm ... .xlsx?dl=0

Hope to get this in the water soon but there are still a few challenges ahead. I look forward to continue hearing what everyone else is doing and discovering. Aloha!

Good stuff. Watching you like a hawk

Seriously guys... I could rant on a very very basic little kid level about how excited for these E-Foils I am.... I mean I was about to just overvolt a trolling motor strapped to a foil for concept before I got into it but look at everyone taking the guesswork out... OOOOOOH pretty soon we are going to be having some fun! I'm a ways out from showing anything just yet =)

Great project. I'll be very interested to see how it works out. It takes a lot of power to get out of the water but once you're up the power requirement should drop quite a bit. The Flyak is able to do it using human power, so with a motor it should certainly be possible.

I've thought about a low power thruster unit for a stand-up paddleboard. Maybe use pressure sensitive pads you stand on to control the thrust and make it sort of self-balancing like a Segway. That one will have to wait until I retire.

It takes about 11kw to get in plane and get good speeds with a normal surfboard like the lampuga. I recently bought a hydrofoil for kitesurfing and there is zo little but of power needed to get good speeds. I just imagine what speeds we will get when we let go the 11kw at a hydrofoil

For years I have been trying many electric outboards etc and one of the things that i found out is that torqeedo is doing a great job, it doesnt even need watercooling. I have a 288rpm kv motor, will gear it down 8 times and put it in the casing of an old trolling motor. I will get about 1500 rpm prop speed. The torqeedo prop speed is 1300, and there prop seems to be very efficiënt. I only wonder when torqeedo prop speed is 1300. Under heavy load or free spinning

Bazaki wrote:It takes about 11kw to get in plane and get good speeds with a normal surfboard like the lampuga. I recently bought a hydrofoil for kitesurfing and there is zo little but of power needed to get good speeds. I just imagine what speeds we will get when we let go the 11kw at a hydrofoil

For years I have been trying many electric outboards etc and one of the things that i found out is that torqeedo is doing a great job, it doesnt even need watercooling. I have a 288rpm kv motor, will gear it down 8 times and put it in the casing of an old trolling motor. I will get about 1500 rpm prop speed. The torqeedo prop speed is 1300, and there prop seems to be very efficiënt. I only wonder when torqeedo prop speed is 1300. Under heavy load or free spinning

With an efficient foil, I think you can get away with a much smaller motor! I would suspect you could even use a max 4kW motor and it would work fine.

The torqeedo 1003 is only 1kW and can achieve a max speed of 9kph at 790W. That would actually be enough to get you up on a good foil.
I worked (roughly) out the motor specs and it would seem that they are as follows:

Bazaki wrote:I know we can foil with less power,.thanks for posting details.
He goes about 30kmh at human power, but i wonder what speeds we will get with 11kw. A foil that can go 60 kmh is much more fun than 30kmh.

I also wonder how much watt we loose from the drag of the casing of the motor. Lets say 40kmh with 10cm diameter but with a sharp edgde

Have you ever had a bad fall waterskiing? I have and you can have a serious impact. Falling at 60kmh from a height of 1m above the sea will hurt like a mother $&*%$£!!

I think the most frustrating part of this project for me is by far trying to find gearboxes. I'd love to experiment with a complete budget build, but gearboxes seem pretty scarce in the UK (and very costly). I am debating whether an adjustable drill gearbox would work...

Bazaki wrote:I know we can foil with less power,.thanks for posting details.
He goes about 30kmh at human power, but i wonder what speeds we will get with 11kw. A foil that can go 60 kmh is much more fun than 30kmh.

I also wonder how much watt we loose from the drag of the casing of the motor. Lets say 40kmh with 10cm diameter but with a sharp edgde

Have you ever had a bad fall waterskiing? I have and you can have a serious impact. Falling at 60kmh from a height of 1m above the sea will hurt like a mother $&*%$£!!

I think the most frustrating part of this project for me is by far trying to find gearboxes. I'd love to experiment with a complete budget build, but gearboxes seem pretty scarce in the UK (and very costly). I am debating whether an adjustable drill gearbox would work...

I will gladly eat it for breakfast lunch and dinner once I have one of these

... it is 86lb thrust though... I see a lot rated at 22kph for 500lb... so... maybe if I overvolt it, strap it to a foil, and sink a 72v test battery into the marine hatch I'll slap in (gotta get the best hatch sourced, important for this IMO)... that's what I was thinking for concept....

The motor is $250... the battery would be laying around... I will use a cheapo digital waterproof remote temp sensor temporarily... I am just trying to left myself up to motivate myself to sink (poor choice of words?) the rest ..... as an alternative if I am too lazy to pull a 'meister' (who is killing it, by the way):

- I print a 3D adaptor to attach the trolling motor directly
- water cool or swap out motor (depending on temps, I'm sure I will have to)
- custom ESC/waterproof remote

but I was so gung ho, like I said, I was just going to strap it to as is! ha

Oh, tell me I am not the only one who was thinking of mounting this into a upside down jet drive on the bottom fin to increase lift! hahahaha. Better get that angle right

The motor is $250... the battery would be laying around... I will use a cheapo digital waterproof remote temp sensor temporarily... I am just trying to left myself up to motivate myself to sink (poor choice of words?) the rest ..... as an alternative if I am too lazy to pull a 'meister' (who is killing it, by the way):

Oh, tell me I am not the only one who was thinking of mounting this into a upside down jet drive on the bottom fin to increase lift! hahahaha. Better get that angle right

What motor is that? There's no link.

There isn't any point in mounting anything vertically. A hydrofoil naturally provides lift once its moving at the correct speed.

So I have looked at a potential budget build.
Looking at eFr3ak's surfboard build, he needed 3.2kW to get it on the plane at +-20kph). On a foil you would be riding on the foil way before reaching the power needed to plane. Therefore I think I may take a risk and go with the following specs as a test unit:

This would give me a similar speed at shaft, but almost twice the power for a cost of around £288.

If the jet drive wont get me enough speed to get out of the water, then I can buy a gear reduction and use a larger prop. This would increase the efficiency a lot, but also increases the cost and as I said, I'm after a budget build.

I have designed a scaled down version of the jet drive with a 37mm impeller (all 3D printed). I tested it with the following specs: 2212 1000kV motor, 30A ESC, 3S battery (10800rpm at 324W). I was quite surprised with how well it performed, hence why I'll start with a jet.

The motor is $250... the battery would be laying around... I will use a cheapo digital waterproof remote temp sensor temporarily... I am just trying to left myself up to motivate myself to sink (poor choice of words?) the rest ..... as an alternative if I am too lazy to pull a 'meister' (who is killing it, by the way):

Oh, tell me I am not the only one who was thinking of mounting this into a upside down jet drive on the bottom fin to increase lift! hahahaha. Better get that angle right

What motor is that? There's no link.

There isn't any point in mounting anything vertically. A hydrofoil naturally provides lift once its moving at the correct speed.

Some Ali supplier... it was an 86lb trolling motor... thought I linked to it. I will find it later, nothing special. I'd copy paste the specs and search it should come right up if you need

Anyway, yeh... I was joking about the upside-down jet drive... thought that was clear

I cant believe I didn't think about this earlier!
From the mockup of the battery for the lift e-foil, one can see that there are 196 cells.
They have also stated that they can achieve around 1hr ride time depending on rider weight.
Therefore they can only be running 7S or 14S
If we then assume a cell capacity of 3400mAh.

In 7S config:
total capacity - 95200mAh
average current draw (for an hour) - 95.2A
average power (using max cell voltage) - 2798.88W

In 14S:
total capacity - 47600mAh
average current draw (for an hour) - 47.6A
average power (using max cell voltage) - 2798.88W

So we can see that the average power draw to keep a rider up on the foil for an hour would be +-2.8kW.

From this it should make it a bit easier to select a motor and then an ESC that will do the job!

I was looking into using an EDF last night. You can get one for $150 that does 4kw. I don't know how those will do in water though. Would a 5 fan blade be better than a 12 fan? I think with a foil it might be better to run high voltage and use an ebike controller. That way the amps are much, much lower. My e-kayak attempts made all my batteries puff as the motor drew such high amps. Recumpence stated on his build that he needed 7500w and blew a couple expensive Castle creations controllers trying to get it worked out. Granted a foil is much more efficient.
Anyhow, I'm going to try and get my e-kayak out again and try running it at 72v with an ebike controller. We'll see if its any better.
I'll try an EDF when I finally learn how to foil.

dirkdiggler wrote:I was looking into using an EDF last night. You can get one for $150 that does 4kw. I don't know how those will do in water though. Would a 5 fan blade be better than a 12 fan? I think with a foil it might be better to run high voltage and use an ebike controller. That way the amps are much, much lower. My e-kayak attempts made all my batteries puff as the motor drew such high amps. Recumpence stated on his build that he needed 7500w and blew a couple expensive Castle creations controllers trying to get it worked out. Granted a foil is much more efficient.
Anyhow, I'm going to try and get my e-kayak out again and try running it at 72v with an ebike controller. We'll see if its any better.
I'll try an EDF when I finally learn how to foil.

There's no doubt about it in my mind that high voltage (HV) and low current makes sense! Just from a battery life point of view it makes all the sense in the world.
I can quite easily see guys blowing ESC's and motors on attempts in this field as it is so easy to over-prop the system. Just reading model boat setups and seeing how many over-prop and blow these components is crazy. Its just mildly frustrating as HV removes any options of a budget build.

I think to keep costs down its definitely worth testing statically with a watt meter to make sure the propulsion system is not over-propped. Once you know you have a sweet spot, then it wont matter if you open it up on the water when testing.

I dont think an EDF will work well in water. Air is much easier to move and props and impellers have a very different design. If you used the EDF casing and motor and re-propped it, it would essentially be a kort nozzle system. I feel it may just be easier to 3D print a better designed system from the get go.

- Aluminium tube for motor housing 60mm OD, 57mm ID
- Hobbyking Yep 120A HV ESC (on special and half the price of the seaking HV) and Yep programmer.
- 6x 2S Lipo's (This will enable me to run a number of different setups and use them on my e-skateboard too)
- 150A Power meter so that I can keep an eye on things!

I think I will most likely go with a 5684 750KV motor at this stage and then its a matter of choosing a gearbox!